Resistance unit



W. ZABEL, DECD.

a. 2mm, AnmmsTn/n'mx.

RESISTANCE UNIT.

APPLICATION FILED JULY 15. m9.

Patented Feb. 15, 1921.

I INVENTOR. mm

A 1 ATTORNEY.

' Swissvale UNITED STATES i a'rei-rr OFFICE.

WILLIAM ZABEL, OE SWISSVALE, PENNSYLVANIA; BERTH A ZABEL, ADMINISTRA-TRIX OF SAID WILLIAM ZABEL, DECEASED, ASSIGNOR TO THE UNION SWITCH &'

SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENN-SYLVANIA.

Specification of Letters Patent.

. Application filed July 15, 1919. Serial No. 311,017.

To all whom it may concern."

Be it known that I, WILLIAM ZABEL, a citizen of the United States,residing at in the county of Allegheny and State of lennsylvania, haveinvented certain new and useful Improvements in Resistance Units, ofwhich the following is a specification.

My invention relates to-resistance units for use in electrical circuits.and particularly to units which are adjustable to vary the value of theresistance imposed'by the unit.

One object of my invention is the provision of a resistance unit whichcan be manufactured economically, and which embodies adequate supportfor the resistance conductor with maximum capacity for radiation. Afurther object of my invention is the provision of a resistance unithaving the aforesaid characteristics and also capable of the maximumnumber of variations in resistance value. v

I will describe one form of resistance unit embodying my invention, andwill then point out the novel features thereof in claims. I

In the accompanying drawings, Figure 1 is a view showing in sideelevation, one form of resistance unit embodying my invention. Fig. 2 isa sectional view on a plane indicated by the line II--II in Fig. 1 andlooking in the direction of the arrows.

Similar reference characters refer to similar parts in each of theviews.

Referring now to the drawings, the reference character 1 designates abase, preferably of insulating material such as porcelain, carrying twospaced terminal posts 2 and 3. Also mounted on the base 1 are twoangular brackets 4 and 5, preferably of 'brass, each having a horizontalportion with a plurality of longitudinal recesses 8 which, as hereshown, are circular in crosssection. As best illustrated in Fig. 2,these Patented Feb. 15, 192 1.

recesses are so located with respect to thesurface of the drum that theyare nearly closed, there being only a narrow slot along the surface ateach recess. The drum is also provided with a circumferential groove 9midway between its ends, as best shown in Fig. 1, the purpose of whichwill appear hereinafter.

Mounted in the recesses 8 is a resistance wire 10 which, as here shown,is in the form of a continuous helix. This wire is threaded back andforth through the recesses 8 with successive strands lying in adjacentrecesses. The resistance wire 10 is of course substantially inclosed bythe recesses near the ends of the drum 6, but each strand is exposed atthe middle of the drum because of the circumferential groove 9.Go-acting with these exposed portions of the several strands is acontact finger 11 which is riveted to a brass strip 12, this strip beingsupported by and in electricalcontact with the terminalpost 3.

One terminal of the resistance wire is electrically connected with thebrass pivot 7 as indicated at 10 and so with the bracket 4 and terminalpost 2. This connection is preferably effected by placing two washers13011 the reduced end portion of the pivot 7 and turning the wire end 10around the pivot between these washers. The other end of the resistancewire is suitably anchored in the drum 6. g It will be evident,therefore, that. when the two terminal posts are connected in anelectric circuit, the amount of resistance which is interposed in thecircuit by the unit may be varied by turning the drum 6 on its axis. Thenumber of adjustments is obviously the-same as the number oflongitudinal strands of wire, that is, there are two adjustments foreach complete loop of wire. It follows that. the unit permits of twiceas many adjustments as would be possible-if the contact finger 11 weremounted for engagement with the wire at one end of the drum or theother. The brackets 4 andf5 are flexible, so that when necessary theycan be spread apart far enough to permit the removal of the drum 6 andthe insertion of a new drum.

A resistance unit embodying my invention provides adequate support forthe resistance wire on the drum, and at the same time it provides formaximum heat radiat- "on said drum with the strands parallel to the axisof the drum and with consecutive strands adjacently located, and acontact mounted to engage with said strands.

2. An adjustable resistance unit comprising a drum mounted to rotate, acontinuous resistance conductor threaded back and forth on said drumwith the strands parallel to the axis of the drum and with theconsecutive strands adjacently located, and a contact mounted to engagesaid strands at a point substantially midway between the ends of thedrum.

3. An adjustable resistance unit comprising a drum mounted to rotate andhaving longitudinal recesses in -its periphery, a resistance conductorthreaded back and forth in said recesses with consecutive strands lyingin adjacent recesses, and a contact mounted to engage said strands at apoint substantially midway between the ends of the drum.

4. An adjustable resistance unit comprising a drum mounted to rotate,said drum having a plurality of longitudinal recesses inv its peripheryand a circumferential groove between the twoends, a resistance conductorthreaded back and forth in said longitudinal recesses with consecutivestrands lying in adjacent recesses, said conductor being substantiallyinclosed by the longitudinal recesses except where it intersects saidcircumferential groove, and a contact mounted to engage the strands ofsaid conductor where they are exposed by the circumferential groove.

5. An adjustable resistance unit comprising a drum mounted to rotate, acontinuous helical resistance conductor threaded back and forth on saiddrum with the strands parallel to the axis of the drum and withconsecutive strands adjacently located, and a contact mounted to engagewith said strands.

6. A resistance unit comprising a cylindrical member of insulatingmaterial having longitudinal recesses in its periphery, and

a resistance conductor threaded back and forth in said recess withconsecutive strands located in adjacent recesses.

7. A resistance unit comprising a cylindrical member of insulatingmaterial having longitudinal recesses in its periphery, and acircumferential groove between its two ends, and a resistance conductorthreaded back and forth in said recesses with consecutive strands lyingin adjacent recesses, said conductor being substantially inclosed by thelongitudinal recesses except where it intersects said circumferentialgroove.

8. An adjustable resistance unit-compris ing a supporting block, twoterminal posts mounted therein, brackets carried on said block and heldin place by said terminal posts, a drum pivoted to rotate in saidbrackets, a resistance conductor mounted on the periphery of said drum,one terminal of said conductor being electricallyconnected with one ofsaid terminal posts through one of the brackets, and a contact fingersupported by the other terminal post and engaging with said resistanceconductor.

9. A resistance unit comprising a supporting block, two spaced bracketsmounted on said block, a drum pivoted to rotate in said brackets, and'aresistance conductor carried by said drum, said brackets being flexibleto permit the removal and insertion ofsaid drum without disturbing themounting of the brackets.

In testimony whereof I afiix my signature in presence of two witnesses.

WILLIAM ZABEL.

Witnesses VVALTIER P. NEUBERT, A. L. VENOILL.

